Predation by Sharks on the Grey Seal (Halichoerus grypus) in Eastern Canada

1983 ◽  
Vol 40 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Paul Brodie ◽  
Brian Beck
Keyword(s):  
Key Words ◽  
Population Size ◽  
Halichoerus Grypus ◽  
Longline Fishery ◽  
Grey Seal ◽  
Eastern Canada ◽  
The Past ◽  
Harbour Seals ◽  
Commercially Important ◽  
Important Fish

The increase in population size of the grey seal (Halichoerus grypus) off eastern Canada over the past 20 yr may be attributed to a decrease in shark stocks, their supposed predators. Reduction of the shark population is presumed to have resulted from a directed longline fishery and, of greater significance, from a change in the fishery for swordfish (Xiphias gladius) from selective harpooning to pelagic longlining, which has produced a large bycatch of sharks. The resulting enhanced survival of grey seals is reflected in greater infestation of commercially important fish species by the codworm (Phocanema decipiens).Key words: grey seals, harbour seals, sharks, swordfish, codworm, predation, fisheries

scholarly journals Historical discarding in Mediterranean fisheries: a fishers' perception

2015 ◽  
Vol 72 (9) ◽  
pp. 2600-2608 ◽  
Author(s):  
Dimitrios Damalas ◽  
Christos D. Maravelias ◽  
Giacomo C. Osio ◽  
Francesc Maynou ◽  
Mario Sbrana ◽  
...  
Keyword(s):  
Species Composition ◽  
Market Demand ◽  
Sampling Protocol ◽  
The Past ◽  
Regulatory Constraints ◽  
Fishing Strategies ◽  
Commercially Important ◽  
Trawl Fisheries ◽  
Important Fish

Abstract Discarding of commercially important fish species in the bottom trawl fisheries in the northern Mediterranean Sea was investigated by soliciting the long-term recollections of fishers engaged or formerly engaged in such fisheries. The main aim of our investigation was to describe the prevalence of discarding and its evolution over the past 70 years using information gathered through individual questionnaire-based interviews with fishers from ports in Spain, Italy, and Greece, following a standardized sampling protocol. Although it proved impossible to derive absolute estimates of the volume of discarded catches over the period investigated, we conclude that over the past 70 years, discarding as a practice has gradually increased in the northern Mediterranean trawl fisheries and has been accompanied by a shift in the species composition of the discarded catch. While discarding can occur for a number of reasons, our investigations indicate that discarding in the past was mostly driven by market demand, but recent legal and regulatory constraints have led to changes in fishing strategies and became a significant reason for discards.

Fatal Interspecies Mating Attempts of a Grey Seal (Halichoerus grypus) with Harbour Seals (Phoca vitulina) on the German North Sea Coast

2020 ◽  
Vol 174 ◽  
pp. 166
Author(s):  
K. Hülskötter ◽  
S. Rohner ◽  
S. Groß ◽  
J. Lakemeyer ◽  
M. Fähndrich ◽  
...  
Keyword(s):  
North Sea ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Harbour Seals ◽  
Sea Coast ◽  
North Sea Coast

scholarly journals Observations on seals on the island of Surtsey in the period 1980-2012

2015 ◽  
Vol 13 ◽  
pp. 41-43
Author(s):  
Erlingur Hauksson
Keyword(s):  
Breeding Site ◽  
Phoca Vitulina ◽  
The Other ◽  
South Coast ◽  
Harbour Seal ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
The South ◽  
Breeding Sites ◽  
Harbour Seals

Grey seals (Halichoerus grypus Fabricius) and harbour seals (Phoca vitulina L.) have been surveyed on the coasts of Iceland since 1980. During the period 1980-2012, both seal species have declined markedly in numbers at the Icelandic coast. The grey seal has established a considerable breeding site on the northern spit of the Surtsey island. This is at present one of the biggest grey seal rookeries on the southern shores of Iceland, with estimated about 60 pups born there in the autumn of 2012. On the other hand, the harbour seal has not been numerous on Surtsey during breeding time in the summer. Breeding sites of harbour seals on the south coast of Iceland closest to Surtsey are in the estuaries of the glacial rivers Ölfusá, Þjórsá, Markarfljót and Kúðafljót. Harbour seals, however, haul-out in great numbers on the northern shores of Surtsey during the winter, presumably using the island as a resting place after foraging in the adjacent waters.

Lungworm (Nematoda: Metastrongyloidea) infections in Canadian phocids

1998 ◽  
Vol 55 (4) ◽  
pp. 825-834 ◽  
Author(s):  
Jean-François Gosselin ◽  
Lena N Measures ◽  
Jean Huot
Keyword(s):  
Detrimental Effect ◽  
Halichoerus Grypus ◽  
Bearded Seal ◽  
Eastern Canada ◽  
New Host ◽  
Ringed Seals ◽  
Phoca Groenlandica ◽  
Harbour Seals ◽  
Young Of The Year ◽  
Otostrongylus Circumlitus

Otostrongylus circumlitus (Railliet, 1899) was found in 5% (16/308) of grey seals (Halichoerus grypus), 6% (1/17; intensity = 38) of harbour seals (Phoca vitulina), and none of 100 harp seals (Phoca groenlandica) from eastern Canada and none of 31 ringed seals (Phoca hispida) from Holman, Northwest Territories. Eighty-two percent of these infections were observed in young-of-the-year seals. Filaroides (Parafilaroides) gymnurus (Railliet, 1899), detected in nodules in the superficial parenchyma of the lungs, infected 24% (5/16) of grey seals, 27% (4/15) of harbour seals, 57% (29/51) of harp seals, 81% (25/31) of ringed seals, and one stranded bearded seal (Erignathus barbatus) (new host report for harp, ringed, and bearded seals; new locality report for Holman). Filaroides (Parafilaroides) hispidus Kennedy, 1986 was found in systematically sliced lungs of grey seals (2/3; new host report) and ringed seals (2/7) but not in harp seals (n = 11) or harbour seals (n = 5). Intensity ranged from 37 to 3570 for F. (P.) gymnurus and from 295 to 1196 for F. (P.) hispidus. No detrimental effect on body condition of seals could be associated with infection by lungworms.

scholarly journals Modelling the abundance of grey seals (Halichoerus grypus) along the Norwegian coast

2012 ◽  
Vol 69 (8) ◽  
pp. 1436-1447 ◽  
Author(s):  
Tor Arne Øigård ◽  
Anne Kirstine Frie ◽  
Kjell Tormod Nilssen ◽  
Mike Osborne Hammill
Keyword(s):  
Confidence Interval ◽  
Population Size ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Norwegian Coast ◽  
Structured Population ◽  
Population Dynamics Model ◽  
Level Model ◽  
Age Structured ◽  
The Uk

Abstract Øigård, T. A., Frie, A. K., Nilssen, K. T., and Hammill, M. O. 2012. Modelling the abundance of grey seals (Halichoerus grypus) along the Norwegian coast. – ICES Journal of Marine Science, 69: . An age-structured population dynamics model of the Norwegian grey seal (Halichoerus grypus) population has been developed. The model is of a Bayesian character in the sense that priors for various parameters were used. Model runs indicated an increase in the abundance of the total Norwegian grey seal population during the last 30 years, suggesting a total of 8740 (95% confidence interval: 7320–10 170) animals in 2011. A total catch of 707 (95% confidence interval: 532–882) grey seals would maintain the population size at the 2011 level. Model runs suggest that current catch levels will likely result in a reduction in the population size in Sør-Trøndelag and Nord-Trøndelag counties, and an increase in the population size in Rogaland, Nordland, Troms, and Finnmark counties. The model runs assumed that 80% of the seals taken in Rogaland came from the UK and that 50 and 55% of the catches in Troms and Finnmark, respectively, were immigrants from Russia.

Mercury in Seals from Eastern Canada

1973 ◽  
Vol 30 (6) ◽  
pp. 843-846 ◽  
Author(s):  
D. E. Sergeant ◽  
F. A. J. Armstrong
Keyword(s):  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Eastern Canada ◽  
Small Pelagic Fish ◽  
Marine Food Web ◽  
Cystophora Cristata ◽  
Pagophilus Groenlandicus ◽  
Harbour Seals ◽  
Order Of Magnitude ◽  
Marine Food

Mercury concentrations in the tissues of four species of seals from individual localities in eastern Canada were highest in liver (usually 1–100 ppm) but up to 387 ppm and lowest in blubber (usually 0.1 ppm). Levels in muscle ranged from < 0.16 to 2.35 ppm. Values similar to those in muscle were found in the few specimens of heart, intestine, and lungs analyzed, and higher values in kidney and hair. Ratios of mercury in the liver to that in the muscle for adult seals were much greater than those found in two species of freshwater fish and three species of domestic animals exposed to wide ranges of mercury concentrations in their food. The ratios for seal pups, however, resembled those in the other animals.Mercury in seals increased with age and appeared to vary with the position in the marine food web of the organisms which they eat. Harp seals (Pagophilus groenlandicus), which feed on small pelagic fish and crustaceans, accumulated an order of magnitude less mercury than grey (Halichoerus grypus) and harbour (Phoca vitulina) seals, which live on large pelagic and benthic fish and cephalopods. However, grey and harbour seals are resident in eastern Canadian waters, which presumably contain higher mercury levels than arctic waters, where harp seals spend about half the year. Yet hood seals (Cystophora cristata), which spent more than half the year in arctic waters but feed on large fish and cephalopods, had mercury levels as high as grey and harbour seals.

Organochlorine Residues in Maternal Blubber, Milk, and Pup Blubber from Grey Seals (Halichoerus grypus) from Sable Island, Nova Scotia

1977 ◽  
Vol 34 (7) ◽  
pp. 937-941 ◽  
Author(s):  
R. F. Addison ◽  
P. F. Brodie
Keyword(s):  
Nova Scotia ◽  
Key Words ◽  
Halichoerus Grypus ◽  
Mammary Tissue ◽  
Milk Lipid ◽  
Grey Seal ◽  
Tissue Concentrations

Residues of DDT group insecticides and of PCBs were measured in samples of maternal blubber, milk, and pup blubber from grey seals (Halichoerus grypus) from Sable Island, N.S. Mean ΣDDT and PCB levels in maternal blubber lipid were 14.0 and 14.5 μg/g, respectively. Concentrations of DDT and PCBs in milk lipid were approximately 60 and 30%, respectively, of those found in maternal blubber lipid, suggesting a partial barrier to passage of these residues through mammary tissue. Concentrations in pup blubber lipid were the same as, or slightly higher than, those in milk lipid.We estimated that a grey seal will lose about 30% of its total ΣDDT burden and about 15% of its PCB burden through lactation; this would be approximately balanced by its estimated annual intake of these residues from food. Thus, the observation that female seals show no increase in residue burdens with age (in contrast to males) is explained. Key words: organochlorine, DDT, DDE, PCB, seal, blubber, milk

The breeding and distribution of the grey seal ( Halichoerus grypus Fab.) in the Baltic Sea, with observations on other seals of the area

1972 ◽  
Vol 182 (1066) ◽  
pp. 37-58 ◽  
Keyword(s):  
Baltic Sea ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Last Deglaciation ◽  
The Baltic Sea ◽  
Eastern Canada ◽  
The North ◽  
Ice Coverage ◽  
Large Numbers ◽  
The Baltic

The grey seal ( Halichoerus grypus Fab.) is considered to be one of the rarest species of the seals. The area of greatest abundance is centred around the coasts of the British Isles where the species has been established for a considerable period. The Grey Seals Acts of 1914 and 1932 gave protection to the species in British waters during the breeding months of September to December. But this seal also occurs in other countries in the North Atlantic, notably in Eastern Canada, often on ice (figures 12, 13, plate 4), Iceland, the Faroes, Norway, the Kola peninsular and the Baltic Sea. The total population is estimated (Smith 1966) to be ca . 52500. Since the last deglaciation considerable changes have occurred in the Baltic region, but at the present time in this tideless sea – which embraces the Gulfs of Bothnia, Finland and Riga, and in waters of a salinity as low as 3.75 ‰, of an area of 400000 km 2 – the grey seal breeds in March on ice, as does the ringed seal in the same month and also on ice, though the common seal breeds in June on sandbanks or rocks. Within the area is a valuable and productive fishery and an inevitable conflict has for long existed between man and the seals, both predators of economically valuable fish, e. g. herring, cod, eel, salmon and other species, leading to the imposition of bounty payments for seals killed. Over the years very large numbers of grey and ringed seals have been killed, chiefly by fishermen in Sweden and Finland, to obtain bounties from the authorities. Unlike the planned culling and undertaken in some British colonies, the Baltic killings have been made at random and little is known of its effect upon the survival of the species. In the Baltic it is not possible to undertake counts of seals owing to the scattered nature of their breeding and the unpredictability of the winter ice coverage.

Grey seal (Halichoerus grypus) predation on harbour seals (Phoca vitulina) on the island of Helgoland, Germany

2015 ◽  
Vol 97 ◽  
pp. 1-4 ◽  
Author(s):  
Abbo van Neer ◽  
Lasse Fast Jensen ◽  
Ursula Siebert
Keyword(s):  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Harbour Seals
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